Washington -LRB- CNN -RRB- -- The U.S. Navy tried to get permission to board a North Korean merchant vessel that it suspected was carrying illicit weapon technology in the South China Sea , the Pentagon confirmed Monday .

It was denied permission , but the United States kept an eye on the vessel , which later turned around and returned to North Korea , the Pentagon said . The incident occurred late last month , it said .

The MV Light is registered and flagged in Belize but was believed to be manned by a North Korean crew , according to Col. David Lapan , a Pentagon spokesman .

According to Lapan , on May 26 , the merchant vessel was hailed by the USS McCampbell , which requested permission to board the ship and inspect its cargo . The ship 's master denied the request , telling the Navy ship that it was a North Korean ship , according to the Pentagon .

Lapan said the vessel was in violation of international law in refusing the boarding .

It was believed the ship might have been heading to Myanmar , he said . Several U.N. resolutions permit the boarding of ships suspected of carrying banned weapons cargo such as ballistic missile parts or technology .

The McCampbell maintained surveillance of the vessel for several days . On May 29 the vessel turned around and headed back to a North Korean port , with the United States maintaining surveillance all the way , Lapan said .

He would not specify how that surveillance was maintained , but the Navy is known to use surveillance aircraft at sea , and U.S. intelligence satellites regularly monitor North Korean ports .

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Permission to board the ship was denied , the Pentagon says

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It was believed the ship might have been heading to Myanmar with banned technology

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The ship eventually returned to North Korea